This invention concerns the field of petroleum refining and, more specifically, processes for converting by hydrogenation heavy crude oils, heavy hydrocarbon cuts and petroleum residues.
The feed charge used in the process of this invention may consist of any heavy hydrocabon oil of high boiling point, for example an oil of which at least 80% by weight of the components have a boiling point above 350.degree. C. The initial oil source may be any hydrocarbon deposit of old origin including, besides crude oil, such materials as shale oil or oil extracted from oily sands, or liquid hydrocarbons obtained by liquefying coal or any hydrocarbon mixture containing undesirable compounds.
The crude oil and the petroleum cuts are very complex mixtures where, in addition to the hydrocarbons, are present various undesirable compounds containing sulfur, nitrogen, oxygen and/or metals. The amount and the nature of the compounds vary in accordance with the origin of the crude oil and the considered cuts. Generally these impurities are detrimental to a good quality of the petroleum products in view of their pollution or corrosion effect, of their odor and/or unstability, or because they make very difficult the refining operations and, particularly, the conversion to light products, since they may deactivate the catalysts used in these conversions such as, for example, the catalytic cracking or hydrocracking catalysts.
The treatment of these charges is made difficult by the presence of asphaltenes and of metals which, under insufficiently controlled conditions, result in the deactivation of the catalysts.
The contaminating metal agents may be present as oxides or sulfides, but usually they consist of organometallic compounds such as porphyrines and their derivatives which are associated to the asphaltenes and to the resins, the most common metals being vanadium and nickel.
The asphaltenes are essentially in the form of a colloidal suspension which, under the hydrorefining conditions, may agglomerate and form a deposit on the catalyst composition. Consequently, the fixed-bed hydrotreatment of these charges does not produce satisfactory results inasmuch as the catalyst deactivates as a result of coke and metal deposition.
A technique for obviating these deficiencies, by providing a better access of high molecular weight asphaltenes to the catalyst sites, is disclosed in several patents, for example the French Pat. No. 1 373 253 or the U.S. Pat. No. 3,165,463.
For this purpose, there are used catalytically active metal compounds, in extremely divided particles, used as a colloidal suspension or dissolved in a solvent. When they are introduced into the charge, they are converted to sulfides and, in the course of the hydrorefining treatment, there is formed a sludge containing the catalyst, asphaltenes and various metal impurities.
It is known to make use as catalytic active agent of a compound of a metal selected from groups II to VIII and, more particularly, from groups IV, V and VI and the iron group. Among the metals of these latter groups, molybdenum is particularly to be mentioned, either alone or in joint use with a metal of the iron group, for example as ammonium heptamolybdate, phosphomolybdic acid, a molybdenum organic salt or molybdenum blue.